Buildings and building systems which use precast concrete structural members are well known. Common components of such buildings and systems are precast concrete beams and columns. Very often, if not usually, precast concrete beams are supported at their opposite ends by concrete columns, or by walls or other parts of the building, defined to receive and support beams. It is well known, even conventional, to support a precast beam between concrete columns by engaging the lower end surfaces of the beam on haunches or ledges formed on the columns as projections which extend laterally from the vertical surfaces of the columns. The weight of the beam and of other building components supported by the beam, and other loads applied in use of the building to the beam and the components supported by it, are carried through the haunches to the columns and by the columns to the column foundations, footings or piers on or in the ground. The beam, as so supported on the columns haunches, is tied into other parts of the building in known ways.
It is now perceived that the common and widespread manner, described above, of supporting precast beams on concrete columns, while reliable and effective and well accepted, does not constitute the best way to provide the necessary beam support. The column must be cast to provide the beam supporting haunches. The forms required for the casting of such columns are more complex and costly than the forms needed for casting simple columns having no haunches; the added complexity and cost is due to the recess which must be present in the column form for the definition of each haunch. The arrangement of reinforcing members embedded in cast columns in the vicinity of a beam support haunch is more complex and costly than for a simple column having no haunches; the added complexity and cost is due to the need to extend substantial portions of the column reinforcing members from locations centrally within the column into the haunches so that loads applied to the haunches can safely be carried into the column itself.
Further, the beam supporting haunches on the column are lateral appendages on the column. The result is that use of column haunches to receive beam loads causes such loads to be applied eccentrically to the column. An eccentrically loaded column is not as strong as the same column when axially loaded, and so an eccentrically loaded column needs more internal reinforcing than does a column designed for the same load applied axially to the column, and the increased internal reinforcement is reflected in the cost to make such a cast column.
Also, when a conventional precast beam is first placed on the haunches of a pair of supporting conventional columns and has not yet been tied into place with other structures, the beam can present a potentially hazardous situation as it merely sits on the column haunches. The beam can be bumped and dislodged from its supports as other parts of the building are moved into place. In that event, workers in the area can be injured, and the beam can be damaged.
It is seen, therefore, that a need exists for an improved way to mount a precast concrete beam to a supporting member such as a cast concrete column or other relevant component of a building of which the beam is a part. This invention addresses that need in a way which has several significant advantages over conventional connections of precast concrete beams to cast columns and the like.